1) How much should installation of a set of FSDs cost? I've read a couple threads saying that it shouldn't be more than $300, but my local shop just quoted me 4-7 hours at $140/hr (not including an alignment after).
4 hours is about right. Labor rate can vary from as long as $60 an hour to $180 an hour depend on where you live.
2) Can someone recommend a good shop in the SF Bay Area that could handle this at a reasonable price?
3) Will there be any demand for my old sport dampers? They'll have less than 30k miles on them. What should I ask for them?
Keep them as you may never know when you need some OE dampers.
4) I plan on keeping my sport springs on the car. Is that ok? Will I need to shorten the bump stops, and if so, will that increase the risk of the wheel contacting the wheel well?
Your OE bump stops are fine, no need to upgrade.